1. Field of the Invention
The present invention relates to a display device. In particular, the present invention relates to improvement of the display quality of a display device capable of bidirectional scanning driving.
2. Description of the Related Art
In a display device, a gate signal line driving circuit, a data signal line driving circuit, and the like control a plurality of pixel circuits provided in a display portion. Generally, the pixel circuits are each provided with a switching element, and, for example, in the case of a liquid crystal display device, the pixel circuits are each provided with a pixel electrode. The switching element is provided between a data signal line extending from the data signal line driving circuit and, for example, the pixel electrode. A switch of the switching element is connected to a gate signal line extending from the gate signal line driving circuit, and the switching element is controlled by a voltage applied to the gate signal line.
The gate signal line driving circuit sequentially outputs, to the plurality of gate signal lines arranged in order, gate signals indicating an ON voltage for a gate signal ON period and an OFF voltage for a gate signal OFF period. When a gate signal output to a gate signal line becomes the ON voltage, a switching element connected to the gate signal line enters the ON state. The data signal line driving circuit supplies a display control voltage corresponding to display data of a pixel circuit including the ON-state switching element, to the data signal line. The display control voltage applied to the data signal line is then applied to the pixel electrode of the pixel circuit via the ON-state switching element. A capacitance is formed between the pixel electrode and a reference voltage. Display of the pixel circuit is controlled by a hold voltage held between the pixel electrode and the reference voltage. Here, a data write period in which the data signal line driving circuit performs write driving of display data into one pixel circuit, namely a period in which a display control voltage corresponding to display data of one pixel circuit is supplied to the data signal line, is referred to as one horizontal period (H).
The demand for higher definition in recent years accompanies difficulty in securing sufficient time for one horizontal period (H). In order to address the problem, gate overlapping driving has been employed to lengthen the gate signal ON period of the gate signal to be longer than one horizontal period (H). In other words, the gate signal ON period of the gate signal contains one corresponding horizontal period (H) and a predetermined period prior thereto.
Further, in order to attain various kinds of image display, a gate signal line driving circuit capable of bidirectional scanning driving has been sought after, which enables both forward scanning driving in which gate signals output to a plurality of gate signal lines arranged in order are controlled to an ON voltage in a direction of the arrangement order and backward scanning driving in which the gate signals are controlled to the ON voltage in a direction reverse to the arrangement order.